/*-
 * Copyright 2003-2005 Colin Percival
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#if 0
__FBSDID("$FreeBSD: src/usr.bin/bsdiff/bsdiff/bsdiff.c,v 1.1 2005/08/06 01:59:05 cperciva Exp $");
#endif

#include <sys/types.h>

#include <bzlib.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define MIN(x,y) (((x)<(y)) ? (x) : (y))

static void split(off_t *I,off_t *V,off_t start,off_t len,off_t h)
{
    off_t i,j,k,x,tmp,jj,kk;

    if(len<16)
    {
        for(k=start; k<start+len; k+=j)
        {
            j=1;
            x=V[I[k]+h];
            for(i=1; k+i<start+len; i++)
            {
                if(V[I[k+i]+h]<x)
                {
                    x=V[I[k+i]+h];
                    j=0;
                };
                if(V[I[k+i]+h]==x)
                {
                    tmp=I[k+j];
                    I[k+j]=I[k+i];
                    I[k+i]=tmp;
                    j++;
                };
            };
            for(i=0; i<j; i++) V[I[k+i]]=k+j-1;
            if(j==1) I[k]=-1;
        };
        return;
    };

    x=V[I[start+len/2]+h];
    jj=0;
    kk=0;
    for(i=start; i<start+len; i++)
    {
        if(V[I[i]+h]<x) jj++;
        if(V[I[i]+h]==x) kk++;
    };
    jj+=start;
    kk+=jj;

    i=start;
    j=0;
    k=0;
    while(i<jj)
    {
        if(V[I[i]+h]<x)
        {
            i++;
        }
        else if(V[I[i]+h]==x)
        {
            tmp=I[i];
            I[i]=I[jj+j];
            I[jj+j]=tmp;
            j++;
        }
        else
        {
            tmp=I[i];
            I[i]=I[kk+k];
            I[kk+k]=tmp;
            k++;
        };
    };

    while(jj+j<kk)
    {
        if(V[I[jj+j]+h]==x)
        {
            j++;
        }
        else
        {
            tmp=I[jj+j];
            I[jj+j]=I[kk+k];
            I[kk+k]=tmp;
            k++;
        };
    };

    if(jj>start) split(I,V,start,jj-start,h);

    for(i=0; i<kk-jj; i++) V[I[jj+i]]=kk-1;
    if(jj==kk-1) I[jj]=-1;

    if(start+len>kk) split(I,V,kk,start+len-kk,h);
}

static void qsufsort(off_t *I,off_t *V,u_char *old,off_t oldsize)
{
    off_t buckets[256];
    off_t i,h,len;

    for(i=0; i<256; i++) buckets[i]=0;
    for(i=0; i<oldsize; i++) buckets[old[i]]++;
    for(i=1; i<256; i++) buckets[i]+=buckets[i-1];
    for(i=255; i>0; i--) buckets[i]=buckets[i-1];
    buckets[0]=0;

    for(i=0; i<oldsize; i++) I[++buckets[old[i]]]=i;
    I[0]=oldsize;
    for(i=0; i<oldsize; i++) V[i]=buckets[old[i]];
    V[oldsize]=0;
    for(i=1; i<256; i++) if(buckets[i]==buckets[i-1]+1) I[buckets[i]]=-1;
    I[0]=-1;

    for(h=1; I[0]!=-(oldsize+1); h+=h)
    {
        len=0;
        for(i=0; i<oldsize+1;)
        {
            if(I[i]<0)
            {
                len-=I[i];
                i-=I[i];
            }
            else
            {
                if(len) I[i-len]=-len;
                len=V[I[i]]+1-i;
                split(I,V,i,len,h);
                i+=len;
                len=0;
            };
        };
        if(len) I[i-len]=-len;
    };

    for(i=0; i<oldsize+1; i++) I[V[i]]=i;
}

static off_t matchlen(u_char *old,off_t oldsize,u_char *new,off_t newsize)
{
    off_t i;

    for(i=0; (i<oldsize)&&(i<newsize); i++)
        if(old[i]!=new[i]) break;

    return i;
}

static off_t search(off_t *I,u_char *old,off_t oldsize,
                    u_char *new,off_t newsize,off_t st,off_t en,off_t *pos)
{
    off_t x,y;

    if(en-st<2)
    {
        x=matchlen(old+I[st],oldsize-I[st],new,newsize);
        y=matchlen(old+I[en],oldsize-I[en],new,newsize);

        if(x>y)
        {
            *pos=I[st];
            return x;
        }
        else
        {
            *pos=I[en];
            return y;
        }
    };

    x=st+(en-st)/2;
    if(memcmp(old+I[x],new,MIN(oldsize-I[x],newsize))<0)
    {
        return search(I,old,oldsize,new,newsize,x,en,pos);
    }
    else
    {
        return search(I,old,oldsize,new,newsize,st,x,pos);
    };
}

static void offtout(off_t x,u_char *buf)
{
    off_t y;

    if(x<0) y=-x;
    else y=x;

    buf[0]=y%256;
    y-=buf[0];
    y=y/256;
    buf[1]=y%256;
    y-=buf[1];
    y=y/256;
    buf[2]=y%256;
    y-=buf[2];
    y=y/256;
    buf[3]=y%256;
    y-=buf[3];
    y=y/256;
    buf[4]=y%256;
    y-=buf[4];
    y=y/256;
    buf[5]=y%256;
    y-=buf[5];
    y=y/256;
    buf[6]=y%256;
    y-=buf[6];
    y=y/256;
    buf[7]=y%256;

    if(x<0) buf[7]|=0x80;
}

int main(int argc,char *argv[])
{
    int fd;
    u_char *old,*new;
    off_t oldsize,newsize;
    off_t *I,*V;
    off_t scan,pos,len;
    off_t lastscan,lastpos,lastoffset;
    off_t oldscore,scsc;
    off_t s,Sf,lenf,Sb,lenb;
    off_t overlap,Ss,lens;
    off_t i;
    off_t dblen,eblen;
    u_char *db,*eb;
    u_char buf[8];
    u_char header[32];
    FILE * pf;
    BZFILE * pfbz2;
    int bz2err;

    if(argc!=4) errx(1,"usage: %s oldfile newfile patchfile\n",argv[0]);

    /* Allocate oldsize+1 bytes instead of oldsize bytes to ensure
    	that we never try to malloc(0) and get a NULL pointer */
    if(((fd=open(argv[1],O_RDONLY,0))<0) ||
            ((oldsize=lseek(fd,0,SEEK_END))==-1) ||
            ((old=malloc(oldsize+1))==NULL) ||
            (lseek(fd,0,SEEK_SET)!=0) ||
            (read(fd,old,oldsize)!=oldsize) ||
            (close(fd)==-1)) err(1,"%s",argv[1]);

    if(((I=malloc((oldsize+1)*sizeof(off_t)))==NULL) ||
            ((V=malloc((oldsize+1)*sizeof(off_t)))==NULL)) err(1,NULL);

    qsufsort(I,V,old,oldsize);

    free(V);

    /* Allocate newsize+1 bytes instead of newsize bytes to ensure
    	that we never try to malloc(0) and get a NULL pointer */
    if(((fd=open(argv[2],O_RDONLY,0))<0) ||
            ((newsize=lseek(fd,0,SEEK_END))==-1) ||
            ((new=malloc(newsize+1))==NULL) ||
            (lseek(fd,0,SEEK_SET)!=0) ||
            (read(fd,new,newsize)!=newsize) ||
            (close(fd)==-1)) err(1,"%s",argv[2]);

    if(((db=malloc(newsize+1))==NULL) ||
            ((eb=malloc(newsize+1))==NULL)) err(1,NULL);
    dblen=0;
    eblen=0;

    /* Create the patch file */
    if ((pf = fopen(argv[3], "w")) == NULL)
        err(1, "%s", argv[3]);

    /* Header is
    	0	8	 "BSDIFF40"
    	8	8	length of bzip2ed ctrl block
    	16	8	length of bzip2ed diff block
    	24	8	length of new file */
    /* File is
    	0	32	Header
    	32	??	Bzip2ed ctrl block
    	??	??	Bzip2ed diff block
    	??	??	Bzip2ed extra block */
    memcpy(header,"BSDIFF40",8);
    offtout(0, header + 8);
    offtout(0, header + 16);
    offtout(newsize, header + 24);
    if (fwrite(header, 32, 1, pf) != 1)
        err(1, "fwrite(%s)", argv[3]);

    /* Compute the differences, writing ctrl as we go */
    if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
        errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
    scan=0;
    len=0;
    lastscan=0;
    lastpos=0;
    lastoffset=0;
    while(scan<newsize)
    {
        oldscore=0;

        for(scsc=scan+=len; scan<newsize; scan++)
        {
            len=search(I,old,oldsize,new+scan,newsize-scan,
                       0,oldsize,&pos);

            for(; scsc<scan+len; scsc++)
                if((scsc+lastoffset<oldsize) &&
                        (old[scsc+lastoffset] == new[scsc]))
                    oldscore++;

            if(((len==oldscore) && (len!=0)) ||
                    (len>oldscore+8)) break;

            if((scan+lastoffset<oldsize) &&
                    (old[scan+lastoffset] == new[scan]))
                oldscore--;
        };

        if((len!=oldscore) || (scan==newsize))
        {
            s=0;
            Sf=0;
            lenf=0;
            for(i=0; (lastscan+i<scan)&&(lastpos+i<oldsize);)
            {
                if(old[lastpos+i]==new[lastscan+i]) s++;
                i++;
                if(s*2-i>Sf*2-lenf)
                {
                    Sf=s;
                    lenf=i;
                };
            };

            lenb=0;
            if(scan<newsize)
            {
                s=0;
                Sb=0;
                for(i=1; (scan>=lastscan+i)&&(pos>=i); i++)
                {
                    if(old[pos-i]==new[scan-i]) s++;
                    if(s*2-i>Sb*2-lenb)
                    {
                        Sb=s;
                        lenb=i;
                    };
                };
            };

            if(lastscan+lenf>scan-lenb)
            {
                overlap=(lastscan+lenf)-(scan-lenb);
                s=0;
                Ss=0;
                lens=0;
                for(i=0; i<overlap; i++)
                {
                    if(new[lastscan+lenf-overlap+i]==
                            old[lastpos+lenf-overlap+i]) s++;
                    if(new[scan-lenb+i]==
                            old[pos-lenb+i]) s--;
                    if(s>Ss)
                    {
                        Ss=s;
                        lens=i+1;
                    };
                };

                lenf+=lens-overlap;
                lenb-=lens;
            };

            for(i=0; i<lenf; i++)
                db[dblen+i]=new[lastscan+i]-old[lastpos+i];
            for(i=0; i<(scan-lenb)-(lastscan+lenf); i++)
                eb[eblen+i]=new[lastscan+lenf+i];

            dblen+=lenf;
            eblen+=(scan-lenb)-(lastscan+lenf);

            offtout(lenf,buf);
            BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
            if (bz2err != BZ_OK)
                errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);

            offtout((scan-lenb)-(lastscan+lenf),buf);
            BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
            if (bz2err != BZ_OK)
                errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);

            offtout((pos-lenb)-(lastpos+lenf),buf);
            BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
            if (bz2err != BZ_OK)
                errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);

            lastscan=scan-lenb;
            lastpos=pos-lenb;
            lastoffset=pos-scan;
        };
    };
    BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
    if (bz2err != BZ_OK)
        errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);

    /* Compute size of compressed ctrl data */
    if ((len = ftello(pf)) == -1)
        err(1, "ftello");
    offtout(len-32, header + 8);

    /* Write compressed diff data */
    if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
        errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
    BZ2_bzWrite(&bz2err, pfbz2, db, dblen);
    if (bz2err != BZ_OK)
        errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);
    BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
    if (bz2err != BZ_OK)
        errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);

    /* Compute size of compressed diff data */
    if ((newsize = ftello(pf)) == -1)
        err(1, "ftello");
    offtout(newsize - len, header + 16);

    /* Write compressed extra data */
    if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
        errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
    BZ2_bzWrite(&bz2err, pfbz2, eb, eblen);
    if (bz2err != BZ_OK)
        errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);
    BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
    if (bz2err != BZ_OK)
        errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);

    /* Seek to the beginning, write the header, and close the file */
    if (fseeko(pf, 0, SEEK_SET))
        err(1, "fseeko");
    if (fwrite(header, 32, 1, pf) != 1)
        err(1, "fwrite(%s)", argv[3]);
    if (fclose(pf))
        err(1, "fclose");

    /* Free the memory we used */
    free(db);
    free(eb);
    free(I);
    free(old);
    free(new);

    return 0;
}
